In recent years, numerous scientific publications and patents have appeared on the use of hydrotalcite-type materials as catalysts in alcohol condensation reactions, such as the Guerbet reaction, in both batch systems and fixed-bed continuous reactors. Most of the reactions described with such catalyst relate to the obtainment of n-butanol from ethanol. The studies performed with these mixed Mg—Al oxides revealed that the catalytic activity of these materials is dependent on the nature, density and strength of the basic surface sites, which, in turn, are dependent on the molar Mg/Al composition in the solid [J. I. Di Cosimo, V. K. Diez, M. Xu, E. Iglesia, C. R. Apesteguia, J. Catal. 178 (1998) 499;
In 1932, the BRITISH INDUSTRIAL SOLVENT Ltd. has claimed in GB381,185 that Mg—Al—Cu mixed oxides showed good activities for ethanol condensation to n-butanol. More recently, it has also established that hydrotalcite-derived mixed oxides based on Cu/Mg/Al show better catalytic activities in alcohols condensation than other analogous hydrotalcites, such as those including Ni supported species [C. Carlini, A. Macinai, M. Marchionna, M. Noviello, A. M. R. Galletti, G. Sbrana, J. Mol. Catal. A: Chem. 206 (2003) 409; X. Jiang, Z. Du, CN101530802 (2009)], among others.
In addition, international application WO2009026510 discloses a process for synthesising n-butanol by means of a material derived from the thermal decomposition of a hydrotalcite which preferably comprises magnesium and aluminium. Moreover, WO2009097312, US20100160693 and WO2009097310 disclose materials obtained by the thermal decomposition of hydrotalcites modified by the inclusion of metal carbonates and ethylenediamine-tetraacetates, which have been developed by DU PONT as catalysts in alcohol condensation reactions operating in a fixed bed at 300° C. and atmospheric pressure. The best results under these conditions have been achieved with a material derived from Cu—Mg—Al-based hydrotalcite (containing OH− as the anion), which presents high ethanol conversion (≈44%) with moderate selectivities (≈44%) to n-butanol. When these same materials were assayed in the catalytic conversion of ethanol into n-butanol in the presence of hydrogen in the reaction system, the yields of n-butanol obtained were significantly lower in all cases.
Synthesis of high molecular weight alcohols (containing between 8-16 atoms of carbon) has become of interest in recent years due to the potential of these oxygenated compounds for use as surfactants and for addition to polymers, lubricants, cosmetics and many other specific uses. In particular, n-hexanol (n-HexOH), with an annual production of 450,000 kilograms, with a low value on the market focused on small scale supply to laboratories, could be transformed into more valuable 1-octanol (1-OctOH) or 1-decanol (n-DeOH).
1-OctOH and n-DeOH, with a world production exceeding 400,000 tonnes per year, are mainly used as surfactants and for addition to polymers, lubricants, cosmetics and many other specific uses.
Currently n-HexOH, produced as an unwanted by-product, is typically used to reduce fuel load in ovens or similar processes. However, increasing the value of n-HexOH by conversion to higher alcohols such as 1-OctOH and DeOH would help to improve the economics of the processes in question.
The 1-octanol can be produced naturally, from fats, oils and waxes of animal or plant origin, as well as synthetically, through petrochemicals such as olefins and paraffins.
The development of catalysts has been of great importance in improving 1-octanol synthesis processes, enabling an increase in yields and a reduction in reaction times, and consequently reducing the costs of these industrial processes. Patent applications EP2679304A1 and EP2679303A1 describe a procedure for obtaining a metal oxide type catalyst that comprises gallium and a noble metal for the process of converting lower alcohols to higher alcohols (specifically methanol, ethanol, propanol or isopropanol to n-butanol) which increases the selectivity of the reaction to n-butanol and productivity of n-butanol. It has been discovered that precisely this type of catalyst, when put in contact with ethanol and n-hexanol, results in the production of higher alcohols, mainly 1-octanol.